Preparation method of DBR reflector and laser

Abstract

The invention discloses a preparation method of a DBR (Distributed Bragg Reflector) reflector. According to the method, the DBR growing on the metal film can be efficiently transferred, and the low-threshold laser can be prepared. Specifically, when the DBR grows in a high-temperature ring, the DBR is self-stripped due to the thermal stress of a metal film, and secondary transfer can be realized by fixing the stripped DBR by using an adhesive tape. According to the method, the limitation of a traditional transfer technology is overcome, self-stripping is realized by utilizing a high-temperature environment when the DBR grows, and the process is simpler and more efficient. The laser prepared by using the transferred DBR can obtain higher performance.

Description

Technical Field

[0001] The invention relates to a preparation method of a DBR reflector and a laser, and belongs to the technical field of super surface optics. Background Art

[0002] Distributed Bragg reflectors (DBRs) are an important component of optical devices. They consist of multiple alternating layers of high and low refractive index materials to form a periodic structure. DBRs are widely used in lasers, fiber-optic communications, optoelectronic devices, optical sensing and other fields due to their high reflectivity, wavelength selectivity, and manufacturing flexibility. DBR reflectors use the Bragg scattering effect to achieve efficient reflection of light of a specific wavelength. When incident light hits the DBR, light diffraction occurs depending on the difference in refractive index between different material layers. Under certain conditions, these diffraction effects cause certain wavelengths of light to be reflected, while other wavelengths of light are transmitted or absorbed.

[0003] DBR laser is a laser based on distributed Bragg reflector (DBR). Its most typical structure is vertical cavity surface emitting laser (VCSEL), which is widely used in optical communication, sensing, lidar and other fields. The main feature of DBR laser is that the reflector of its resonant cavity is composed of DBR layer, which can achieve narrow bandwidth laser output by selectively reflecting light of specific wavelength. When current is injected into the active layer, electrons and holes recombine to generate photons, which are reflected back and forth between the DBR reflectors. The active layer provides gain to amplify the optical signal. When the wavelength of light matches the Bragg condition of the DBR reflector, the reflectivity reaches the maximum, a stable resonance is formed in the cavity, and laser is output from the top DBR.

[0004] Compared with the traditional substrate structure, the substrate-free distributed Bragg reflector (DBR) eliminates the influence of the substrate on the optical performance, making the DBR achieve higher reflectivity and more precise optical properties in a wider wavelength range. DBRs grown on substrates will encounter greater difficulties during transfer, and the DBR layer will be directly damaged when the substrate is peeled off. For example, SiO grown directly on a silicon substrate 2 / When transferring SiN stacked DBR, wet etching the silicon substrate will react with SiO2 and damage the DBR layer. Therefore, we need a transfer method that does not damage the DBR layer and has a simple process. Summary of the invention

[0005] The invention discloses a method for preparing a DBR reflector, which overcomes the problem of poor effect of damaging a DBR layer when transferring the DBR by wet etching a substrate, realizes complete transfer of the DBR, and ensures its high reflection performance and structural integrity.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing a DBR reflector, comprising the steps of:

[0008] (1) Evaporating a metal thin film layer on a substrate;

[0009] (2) Annealing the metal film layer in N2 atmosphere;

[0010] (3) Using PECVD equipment to grow a DBR structure on the metal film layer;

[0011] (4) The thermal stress of the metal film is used to make the grown DBR peel off by itself.

[0012] Preferably, step (4) specifically refers to sticking the DBR with tape before cooling. Generally speaking, the tape can be applied after the growth of the DBR is completed, and the DBR is transferred to the desired device after the temperature naturally drops to room temperature. The metal film has a significantly different thermal expansion coefficient from the DBR growth material, which will cause stress accumulation between the material layers during the high-temperature growth process, thereby causing the DBR and the metal film layer to self-peel after cooling. Using tape to stick the DBR can maintain the integrity of the DBR.

[0013] Preferably, step (2) is specifically: treating the metal film by rapid annealing at 300-500° C. for 5 to 15 minutes in a nitrogen atmosphere.

[0014] Preferably, the metal film layer is made of gold, silver or nickel, and has a thickness of 10-100 nm.

[0015] Preferably, the DBR is formed by stacking a low refractive index layer and a high refractive index layer, wherein the low refractive index layer / high refractive index layer is selected from SiO2 / TiO2, SiO2 / Si3N4 or AlGaN / SiO2, the thickness of each layer is 10-50nm, and the number of stacked layers is 4 to 100 layers, wherein the number of stacked layers refers to the sum of the number of low refractive index layers and the number of high refractive index layers.

[0016] Preferably, the growth temperature of DBR is 150-350°C.

[0017] The DBR reflector is prepared by the above-mentioned method for preparing the DBR reflector.

[0018] The invention also discloses a laser, which is made of the DBR reflector.

[0019] The beneficial effects of the present invention are:

[0020] 1. By controlling the deposition parameters of the PECVD equipment and the annealing conditions of the metal film, the DBR is effectively separated from the metal substrate, which simplifies the process and improves production efficiency.

[0021] 2. The method of the present invention avoids the damage to the DBR that may be caused when removing the substrate by wet etching through the thermal stress self-stripping mechanism, thereby ensuring the integrity and optical performance of the reflector layer.

[0022] 3. The fixing effect of the tape during the peeling process further enhances the stability of the DBR structure, ensuring its mechanical strength and optical consistency in subsequent transfer and application.

[0023] 4. The transferred substrate-free DBR can be made into higher performance optical devices and can be used to prepare low threshold lasers.

[0024] 5. The method of the present invention has wide applicability and can be used not only for DBR preparation and transfer, but also for the manufacture of thin film devices on other complex substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the method for transferring a DBR grown on a metal substrate.

[0026] Figure 2 Schematic diagram of the structure after growing a metal film on a substrate.

[0027] Figure 3 Schematic diagram of the structure after DBR is grown on the metal film.

[0028] Figure 4 Schematic diagram of the structure of DBR after self-stripping.

[0029] Figure 5 This is a schematic diagram of the structure of the low threshold laser made in Example 1.

[0030] Figure 6 Schematic diagram of the DBR laser structure prepared by the traditional patch method in comparative example 1.

[0031] Figure 7 This is a photograph of the transferred DBR prepared in Example 1.

[0032] Figure 8 This is a photograph of the transferred DBR prepared in Comparative Example 1.

[0033] Fig. 9 This is a diagram of the threshold data of the low-threshold laser obtained in Example 1.

[0034] Fig.10 This is the spectrum diagram of the low threshold laser prepared in Example 1.

[0035] Fig.11 This is a graph of the DBR laser threshold data obtained in Comparative Example 1.

[0036] Fig.12This is the spectrum diagram of the DBR laser prepared in Comparative Example 1.

[0037] Description of the markings in the figure:

[0038] 1: Silicon substrate

[0039] 2: Metal film

[0040] 3: DBR layer prepared by stacking low refractive index layer and high refractive index layer

[0041] 4: Tape

[0042] 5: Perovskite quantum dot film

[0043] 6: GaAs substrate. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with embodiments, but the description of the embodiments does not impose any limitation on the protection scope of the present invention.

[0045] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention, and the terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. In addition, although demonstrations of parameters containing specific values ​​may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint. The directional terms mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only directions with reference to the accompanying drawings. Therefore, the directional terms used are used to illustrate rather than to limit the scope of protection of the present invention.

[0046] Unless otherwise specified, the materials and instruments used in the following examples can be obtained from conventional commercial channels.

[0047] Example 1 A method for preparing a low threshold laser using a transferred DBR reflector:

[0048] (1) In this embodiment, a silicon wafer is selected as the substrate and the silicon wafer is cleaned. The cleaning process is as follows: the silicon wafer is placed in an acetone solution for ultrasonic treatment for 10 minutes, then placed in an ethanol solution for ultrasonic treatment for 10 minutes, then rinsed with deionized water, and blown dry.

[0049] (2) Figure 2 As shown, a gold (Au) thin film with a thickness of 50 nm is evaporated on a silicon substrate using an electron beam evaporation device (EBE).

[0050] (3) The gold film was annealed in a rapid annealing furnace (RTP) to eliminate stress. The annealing conditions were as follows: in a N2 atmosphere, the temperature was raised from room temperature to 500°C in 30 seconds, maintained for 5 minutes, and then cooled to room temperature in 30 seconds.

[0051] (4) Figure 3 As shown, a plasma enhanced chemical vapor deposition (PECVD) device is used to grow the DBR layer. In this example, the low refractive index layer (L layer) is selected to be SiO2, with a thickness of 25nm and a refractive index of 1.46; the high refractive index layer is selected to be Si3N4, with a thickness of 15nm and a refractive index of 2.05. The conditions for PECVD growth of SiO2 are as follows: a 5% SiH4 / N2 mixed gas and N2O gas are introduced into the reaction chamber with flow rates of 100 sccm and 400 sccm respectively, and SiO2 is deposited on the substrate surface at a pressure of 300 mTorr, a power of 10 W, and a temperature of 350°C for 70 s; the conditions for PECVD growth of Si3N4 are as follows: a 5% SiH4 / N2 mixed gas, NH3 gas, and N2 gas are introduced into the reaction chamber with flow rates of 25 sccm, 20 sccm, and 400 sccm respectively, and Si3N4 is deposited on the substrate surface at a pressure of 500 Torr, a power of 50 W, and a temperature of 350°C for 100 s.

[0052] (5) Repeat step (4) 26 times to complete the deposition of the DBR. The resulting DBR has a 54-layer stacked structure.

[0053] (6) Figure 4 As shown in Figure 2, the DBR grown at 350°C in this example will peel off due to the thermal stress of the metal. Figure 1 As shown, the DBR is adhered with tape for secondary transfer. Figure 7 and Figure 8 Take a picture of the DBR being transferred in the lab.

[0054] (7) Figure 5 As shown in the figure, a MAPbBr3 perovskite solution is spin-coated on a transferred DBR, and then another transferred DBR is covered on it to make a vertical cavity surface emitting laser (VCSEL), with the active area being perovskite quantum dots. Fig. 9 and Fig.10 As shown, the threshold of the fabricated DBR laser is significantly reduced.

[0055] Comparative Example 1 A method for preparing a DBR laser using a patch method:

[0056] (1) In this comparative example, GaAs and silicon wafers were selected as substrates for two groups of DBRs, respectively. The substrates were cleaned. The cleaning process was as follows: the substrates were placed in an acetone solution for ultrasonic treatment for 10 minutes, then placed in an ethanol solution for ultrasonic treatment for 10 minutes, then rinsed with deionized water, and dried.

[0057] (2) Figure 3 As shown, a plasma enhanced chemical vapor deposition (PECVD) device is used to grow the DBR layer. In this example, the low refractive index layer (L layer) is selected to be SiO2, with a thickness of 25nm and a refractive index of 1.46; the high refractive index layer is selected to be Si3N4, with a thickness of 15nm and a refractive index of 2.05. The conditions for PECVD growth of SiO2 are as follows: a 5% SiH4 / N2 mixed gas and N2O gas are introduced into the reaction chamber with flow rates of 100 sccm and 400 sccm respectively, and SiO2 is deposited on the substrate surface at a pressure of 300 mTorr, a power of 10 W, and a temperature of 350°C for 70 s; the conditions for PECVD growth of Si3N4 are as follows: a 5% SiH4 / N2 mixed gas, NH3 gas, and N2 gas are introduced into the reaction chamber with flow rates of 25 sccm, 20 sccm, and 400 sccm respectively, and Si3N4 is deposited on the substrate surface at a pressure of 500 Torr, a power of 50 W, and a temperature of 350°C for 100 s.

[0058] (3) Repeat step (2) 26 times to complete the deposition of DBR.

[0059] (4) Figure 6 As shown, two DBR structures are firmly bonded together using a hot pressing process to form the final laser cavity structure, with the active region being a GaAs substrate.

[0060] (5) After the spectrometer test, the results are as follows Fig.11 and Fig.12 As shown, compared with Example 1, the threshold of the low-threshold laser prepared using the transferred DBR reflector has a significant decrease.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a DBR reflector, characterized in that The steps include: (1) Evaporating a metal thin film layer on a substrate; (2) Annealing the metal film layer in N2 atmosphere; (3) Using PECVD equipment to grow a DBR structure on the metal film layer; (4) The thermal stress of the metal film is used to make the grown DBR peel off by itself.

2. The method for preparing a DBR reflector according to claim 1, characterized in that: Step (4) specifically refers to sticking the DBR with tape before cooling, and transferring the DBR to the desired device after it is naturally cooled to room temperature.

3. The method for preparing a DBR reflector according to claim 1 or 2, characterized in that: Step (2) is specifically: in a nitrogen atmosphere, the metal film is rapidly annealed at 300-500° C. for 5-15 min to eliminate the intrinsic stress of the growing metal film.

4. The method for preparing a DBR reflector according to claim 1 or 2, characterized in that: The metal film layer uses metal gold, silver or nickel, and has a thickness of 10-100nm.

5. The method for preparing a DBR reflector according to claim 1 or 2, characterized in that: The DBR is formed by stacking a low refractive index layer and a high refractive index layer, wherein the low refractive index layer / high refractive index layer is selected from SiO2 / TiO2, SiO2 / Si3N4 or AlGaN / SiO2, the thickness of each layer is 10-50nm, and the number of stacked layers is 4 to 100.

6. The method for preparing a DBR reflector according to claim 5, characterized in that: The number of stacked layers of the DBR is 20-100.

7. The method for preparing a DBR reflector according to claim 5, characterized in that: The growth temperature of DBR is 150-350℃.

8. A DBR reflector made by the method for making a DBR reflector according to any one of claims 1 to 7.

9. A laser, characterized in that Made of the DBR reflector as claimed in claim 8.

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